软土盾构隧道纵向设计综述

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1、-软土盾构隧道纵向设计综述-摘要:通过对软土盾构隧道构造设计理论的现状和已建软土盾构隧道构造存在问题的分析,指出抑制软土盾构隧道构造发生过量纵向沉降或不均匀沉降而引起隧道渗水、漏泥、构造局部破坏等影响隧道正常使用及其耐久性问题的关键是展开纵向设计理论研究。在纵向设计理论指导下,通过软土盾构隧道衬砌管片拼装形式、管片材料等方面的创新改造,使软土盾构隧道的设计方法更加科学合理。关键词:软土;盾构隧道;纵向设计;地下工程1概述随着世界经济的全球化和社会的不断进步,人们对自身的生存环境质量的要求愈来愈高,致使城市化水平迅速提高,城市规模不断扩大。城市成为世界各国、各地区的政治、经济、文化开展中心。然而

2、,为城市建立的可持续开展、资源的节约和环境的保护,城市建立者越来越多地开发利用一切可以利用的有限生存空间,尤其是城市的地下空间,以建立给水、排水、能源、交通等地下隧道。然而,随着地下空间的开发利用,越来越多的地下构造由于使用过程中的过量不均匀变形而致的对地下构造本身及其周围环境的影响也愈加严重12。例如,在地下动水压力的作用下,*市金山海水引水工程中的盾构隧道(见图1)下卧土层的水土流入隧道,隧道随之产生纵向沉降和弯曲,导致环向接缝进一步*开和水土流失增加,最终导致破坏性纵向变形和破坏性横向受力状态,最大相对不均匀沉降到达了18,横向直径变化最大超过103。*市地铁一号线于1995年4月正式建

3、成投入运营。经过长期的变形监测发现,隧道在长期运营中的沉降及不均匀沉降相当大,许多隧道段的沉降和不均匀沉降一直在开展,而且没有收敛的趋势4。至2001年底人民广场站-新闸路站之间的区间隧道最大累计沉降量超过200;黄陂南路站-人民广场站之间的区间隧道差异沉降量近100(详见图2)。过大的不均匀变形已对隧道的构造、接头防水构成威胁。到目前为止,虽然管片遭到破坏的情况极少,但在一号线已发现道床与管片之间发生开裂现象,在*路站至黄陂南路站之间已经发现至少5处整体道床与管片之间发生开裂和脱节现象,断断续续累计达300。经过调查发现,根本上都是由于隧道局部较大的不均匀沉降造成5。另外由于纵向不均匀变形造

4、成管片接缝变形增大,一号线的区间隧道渗漏水的地方很多,漏水点主要集中在环缝、封顶块相连的“十字缝等处,而环缝漏水是最难处理的。随着隧道纵向不均匀变形的开展,隧道漏水的情况越来越多,甚至会影响地铁的正常运营。当前大量地下隧道建立实践中,盾构施工法已成为城市地下隧道建立的主要施工方法,尤其地铁隧道。*现有和正建的地铁隧道无一例外地采用这一方法施工。而*同许多沿海城市一样是位于软土广泛分布的地层上,正是盾构隧道构造所处的软土环境导致大量的运营软土盾构隧道发生过量的纵向沉降或不均匀沉降,引起隧道渗水、漏泥或构造局部破坏,有时甚至会影响到隧道的正常运营2021。因此,深入研究软土盾构隧道纵向变形对隧道构

5、造影响及考虑纵向变形的衬砌构造纵向设计理论是解决软土盾构隧道现存问题的关键,尤其是衬砌构造纵向设计方法。2衬砌构造纵向设计现状目前,国内外对盾构法隧道衬砌构造设计主要采用横向设计。在国内,我国地下铁道及铁路隧道设计规*6中推荐使用荷载构造模型,而未考虑纵向变形的影响。?*市地基根底设计规*?1999版中对盾构隧道纵向变形进展了一定的考虑7,提出盾构隧道纵向不均匀沉降的影响是不可无视的。尤其是盾构工作井和区间隧道的连接处;隧道底部下卧土层特性及分层突变处;覆土厚度急剧改变处等,都会有较明显的不均匀沉降。提出在设计中应按照预估的沉降差,设置适量的变形缝。规*还提到在施工阶段和使用阶段,进展隧道构造

6、的横向内力和变形计算时,在必要的时候宜考虑隧道纵向变形对横向内力和变形值的影响。目前,国内针对软土盾构法隧道采用的设计模型主要为匀质圆环和弹性铰法1317,皆可用弹性方程解。前者主要用于使用阶段的设计验算,后者主要用于施工阶段的设计验算。在国外,国际隧道协会()在1978年成立了隧道构造模型研究组,收集各会员*用的地下构造设计模型。并于2000年编写出了?盾构隧道衬砌设计指南?8,为各国盾构隧道构造的设计指明了根本原则。其中将构造模型分为四类:连续体或不连续体模型、作用与反作用模型、收敛-约束模型和工程类比法。这与我国学者*、侯学渊5的分类(经历类比模型;荷载构造模型;地层构造模型;收敛限制模

7、型)根本一样。同时在?盾构法隧道设计指导?中提出在必要时将隧道纵向沉降的影响列入荷载类别的特殊荷载项予以考虑。美国交通运输研究协会在2000年度报告9中就提到,很多处于软土中的隧道、管道的破坏或出现问题就是由于纵向不均匀沉降而产生的。最多的一种情况就是由于下卧土层土性沿纵向分布不均匀而产生的纵向不均匀沉降。因此美国交通运输研究协会在2000年提出了隧道“纵向设计的概念,并方案开场进展这方面的研究工作。由此可见,在现行的设计规*中还没有纵向设计的相关内容,但是,构造的纵向问题对构造的影响已经引起广阔学者关注。因此,开展纵向设计相关研究具有重大现实意义。免费论文下载中心.hi138. 由于隧道纵向

8、问题属于三维问题,其构造复杂,纵向构造计算模型尚不成熟。但也已经取得了一定的科研成果。在工程实测和室内试验根底上,已建立了一些隧道纵向构造计算模型。目前对软土隧道纵向构造的理论研究主要分为:试验或实测分析法、数值分析法和理论解析法。在理论解析法中根据隧道接缝和螺栓简化方法的不同,日本学者提出了两种隧道纵向构造理论,一种是以村上博智及小泉淳22为代表的以轴向、剪切和弯曲弹簧模拟接缝和螺栓、以梁单元模拟衬砌环的梁一弹簧模型,它是将横向梁一弹簧模型移植到了隧道构造纵向(见图3);纵向粱一弹簧模型中每一衬砌环均由一直线粱模拟,各衬砌环间的接缝以弹簧模拟,因而在作纵向分析计算时单元较多,它可以模拟衬砌环

9、和接缝性能有变化的隧道段,但其缺点也是明显的,即一般适合于线性分析,并且由于以单元作为根底,分析过程为矩阵形式,需要通过数值方法实现,所得结果需要进展再一次分析才能得到管片、螺栓应力和接缝*开度等关键数据。另一种模型是以志波由纪夫及川岛一彦2325为代表的等效轴向刚度模型,该方法认为隧道在横向为一均质圆环、在纵向以刚度等效的方法将有环向接缝非连续的构造等效为连续均质圆筒。由于是直接从分析衬砌环向接缝和螺栓的受力变形性能出发得到等效模型,因此计算结果可直接给出管片和螺栓应力,并且在很多情况下可推导得到显式理论解,应用方便,但该方法也有未考虑预应力、只简单被认为是弹性地基上的直梁等缺点,然而,根据

10、目前国内外的研究现状来看,轴向等效刚度方法是当前隧道构造的纵向理论研究中提出的最好的方法。该法为研究盾构隧道纵向问题奠定了坚实的理论根底。 3盾构隧道构造拼装型式盾构隧道构造是由管片在环向和纵向通过螺栓连接而成的非连续构造。由于预制钢筋混凝土管片经济、耐久及强度高,所以成为目前国内外的盾构法隧道管片的主要形式。盾构隧道衬砌构造拼装型式有两种:错缝拼装衬砌与通缝拼装衬砌10111219。这两种拼装型式的不同之处在于;错缝拼装衬砌由于相邻环管片间构造刚度沿环向分布的不同,虽然受到的初始荷载根本一样,但构造变形却不同、引起的地层反力不同,地层反力的不同又加剧了构造变形的不同。由于相邻环之间存在联系,

11、如连接螺栓、环面凹凸榫槽和环面间的摩擦又阻碍了构造变形的不同,使构造变形与荷载及地层反力分布的不同限于一定的*围之内。而通缝拼装衬砌由于相邻环管片间构造刚度沿环向分布一样,受到的初始荷载也根本一样。因此,构造变形根本一样、引起的地层反力也根本一样。虽然,通缝拼装衬砌每一环横向变形也受到相邻环的嵌固和约束,但这种约束和影响的效应错缝比通缝更显著。衬砌环间的这种相互作用非常复杂,因此错缝衬砌内力与变形的计算也比较复杂,其计算模型与计算方法还在深入研究之中。在我国,*先期施工的盾构法隧道根本采用通缝拼装形式,而*近期建立的隧道及*和*地铁盾构法隧道则全部采用错缝拼装形式,从而说明错缝拼装形式在抵抗纵

12、向变形上优于通缝拼装形式。既然不同的拼装形式有不同力学效果,能够改变衬砌的纵向刚度及控制纵向裂缝和不均匀变形,则采用更多不同力学效果的拼装形式就成为解决当前软土盾构隧道构造纵向问题的另一关键问题。4软土盾构隧道构造存在问题从当前工程设计的实际应用和理论研究进展分析可得出软土盾构隧道衬砌构造在考虑纵向问题时的缺乏之处:缺乏与纵向理论要求接近的衬砌形式;现有的纵向理论缺乏与工程实际的结合;衬砌拼装形式单一(不能协调纵向不均匀变形);衬砌管片材料在同一工程中单一;衬砌管片宽度在同一工程中单一;纵向线形不合理。5软土盾构隧道纵向设计展望为抑制软土盾构隧道现存问题,必须从以下两方面来解决:(1)从软土盾

13、构隧道衬砌管片拼装形式、管片材料等方面进展创新改造。以增大软土盾构隧道衬砌构造的纵向刚度的变化,使软土盾构隧道衬砌构造的纵向刚度具有可控性。而不同刚度的多样的衬砌构造拼装形式是解决软土盾构隧道纵向问题成为可能。(2)在纵向设计理论研究及其成果应用上应有所加强。隧道纵向构造性能的研究和横向性能研究相比还处在早期开展阶段,其成果尚未应用到工程设计的实践中。如何将已有的理论研究成果应用于工程设计(即纵向设计),使工程设计更加符合客观现实。这不仅符合当前设计理论开展的趋势,更能实现在设计阶段上就开场着手解决软土盾构隧道现存问题(过量的纵向沉降或不均匀沉降,导致隧道渗水、漏泥或构造局部破坏而影响隧道的正

14、常运营),防止软土盾构隧运营后再进展处理的被动状态,因此,可节约大量资金。总之,软土盾构隧道构造纵向设计理论,不仅是软土盾构隧道构造设计理论开展的需要,也是社会开展的需要。它不仅具有理论价值,而且更具重要的经济意义和社会意义。Design of Shield Tunnel in Soft Soil Longitudinal Survey Abstract: Based on soft soil shield tunnel structure design theory, the current situation and have been built there is soft soil s

15、hield tunnel structure analysis of the problems, pointing out that to overe the soft soil shield tunnel in the structure of vertical settlement of e*cessive or uneven settlement caused by the tunnel seepage, leakage mud, the impacts of the tunnel structure, partial destruction of the normal use and

16、durability The key is to start longitudinal study of design theory. Under the guidance of the longitudinal design theory, through the soft soil shield tunnel lining segment assembled form, the segment in innovation and transformation of materials, so that the design of soft soil shield tunnel method

17、 is more scientific and rational. Key words: soft soil; shield tunnel; longitudinal design; underground engineering 1 Overview As the world economy, globalization and social progress, people have their own quality of living environment of rising demand, resulting in rapid increase in the level of ur

18、banization, cities have been e*panding. Cities bee the worlds countries and regions of political, economic and cultural development centers. However, to the sustainable development of urban construction, resource conservation and environmental protection, urban development and utilization of more an

19、d more builders of all can take advantage of the limited living space, especially in urban underground space, in order to build water supply, drainage, energy and transport underground tunnel. However, with the development and utilization of underground space, a growing number of underground structu

20、res due to the use of the process of non-uniform deformation caused the e*cess of the underground structure itself and the surrounding environment has bee even more serious 1 2. For e*ample, in the ground under the effect of hydrodynamic pressure, the Shanghai Jinshan water diversion project in the

21、shield tunnel (see Figure 1), the horizontal layers of soil and water into the tunnels and the resulting vertical settlement and bending, resulting in circumferential seams further open and soil erosion increased, eventually lead to devastating and destructive horizontal vertical deformation force s

22、tatus, the ma*imum relative differential settlement reached 18cm, the largest transverse diameter of more than 10cm 3. Shanghai Metro Line in April 1995 formally pleted and put into operation. After long-term deformation monitoring found that the tunnel in the long-term operation of the settlement a

23、nd differential settlement quite large, many of the tunnel section of settlement and differential settlement has been developing, and there is no trend of convergence 4. To the end of 2001 the Peoples Square station - the interval between the *inzha Station tunnel ma*imum total settlement of more th

24、an 200mm; Huangpi Station - the Peoples Square Station tunnel differences in the interval between the settlement of nearly 100mm (see Figure 2). Too much has been uneven deformation of the structure of the tunnel, joint water threat. So far, although the segment of the destruction of rare, but on th

25、e 1st line has been found between the ballast and tube sheet cracking phenomenon occurring in the Hanzhong Road Station to Station Huangpi of at least five have been found between the overall track bed and segment and the gap between the cracking phenomenon, intermittent totaled 300m. After investig

26、ation found that are basically a large part due to uneven settlement of the tunnel caused by 5. In addition, as the vertical deformation caused by uneven deformation of the segment joints increases, on the 1st line of the tunnel ranges in many areas of water seepage and leaking points, mainly in gir

27、th, cap connected to the block of cross-stitch, etc., while the ring seam leakage is the most difficult to deal with. With the development of uneven deformation of the vertical tunnel, tunnel leakage increasing number of cases, and even affect the normal operation of the MTR. The current practice of

28、 building a large number of underground tunnels, the shield construction method has bee a major urban underground construction method of tunnel construction, particularly in metro tunnels. Shanghais e*isting subway line and is being built using this method of construction without e*ception. In Shang

29、hai, like with many coastal cities are located in soft soil strata are widely distributed on the shield tunnel structure is the soft soil environment in which a large number of operations leading to soft soil Shield Tunnel e*cessive vertical settlement or differential settlement, causing the tunnel

30、water seepage, leakage or structural partial destruction of mud, and sometimes affect the normal operation of the tunnel 20 21. Therefore, the in-depth study of soft soil shield tunnel longitudinal deformation of the tunnel structure and consider the impact of the vertical structure of vertical defo

31、rmation of the lining of the design theory to solve the e*isting problems of soft soil shield tunnel key, in particular the vertical lining structure design methods. Two vertical lining structure design of the status quo At present, the right domestic and international structural design of shield tu

32、nnel lining used mainly horizontal design. In China, Chinas Mass Transit Railway and the railway tunnel design specification 6 remended the use of load structure model, without considering the impact of vertical deformation. Shanghai-based foundation design code 1999 version of the vertical deformat

33、ion of shield tunnel, which must be considered 7, proposed shield tunnel longitudinal impact of uneven settlement can not be ignored. Especially the shield work well and interval tunnel junction; tunnel lying under the bottom layer of soil characteristics and mutation Branch; Futuhoudu drastically c

34、hanged Department, will have a more significant differential settlement. Made in the design should be in accordance with the estimated differential settlement, set an appropriate amount of deformation crack. Specification also referred to in the construction phase and use phase of the tunnel structu

35、re, the horizontal internal force and deformation calculation, when necessary, should take into account the vertical deformation of the tunnel horizontal internal force and deformation effects. At present, the domestic soft soil for the shield tunnel design models used primarily for homogeneous ring

36、 and fle*ible hinge method 13 17 may apply to use elastic equations. The former is mainly used for checking the use of stage design, which is mainly used for checking the construction stages of the design. In other countries, the International Tunneling Association (InternationalTunnelAssociation) w

37、as established in 1978, the tunnel structure model of study groups, the collection of all Member States to adopt the underground structure design model. And in 2000 prepared a Shield Tunnel Lining Design Guide 8, for countries to shield the design of the tunnel structure pointed out the basic princi

38、ples. Structural model which will be divided into four categories: a continuum or continuum model, the role and reaction models, convergence - a constraint model and engineering analogy. This Chinese scholars Liu Hang, Hou *ieyuan 5 classification (e*perience in analog model; load structure model; s

39、tratigraphic structure model; convergence limit model) basically the same. At the same time in the shield tunnel design guidelines when necessary, will be proposed in the settlement of the tunnel vertical load categories included in the special load options to be considered. U.S. Transportation Rese

40、arch Institute at the 2000 annual report 9 mentions that many in the soft soil of the tunnel, pipeline damage or problems that arise due to uneven settlement of the vertical. Up to a situation that is lying under the soil due to its rural character and unevenly distributed along the longitudinal dif

41、ferential settlement resulting from the vertical. Therefore, the U.S. Transportation Research Institute in 2000 to the tunnel longitudinal design concept, and plans to start research work in this area. This shows that in the current design codes are also not related to the contents of the vertical d

42、esign, but the structure of the vertical structure of problem has attracted broad attention and scholars. Therefore, to carry out longitudinal research design is of great practical significance. Reposted elsewhere in the paper for free download .hi138. As the tunnel vertical issues are three-dimensi

43、onal problem, its ple* structure, vertical structure calculation model is not yet ripe. But it has also made some achievements in scientific research. In engineering measurement and laboratory test, based on a number of tunnels have been established model of the vertical structure calculation. Prese

44、nt the vertical structure of soft soil tunnel theoretical study can be divided into: testing or measurement analysis, numerical analysis and theoretical analysis method. In theory, analytical method, in accordance with the tunnel joints and bolt to simplify the different methods, the Japanese schola

45、rs have put forth a theory of vertical structure of the two tunnels, one is based on Chi and Koizumi, Atsushi Murakami 22 as the representative to a*ial, shear and bending spring simulation joints and bolts, in order to beam element simulation of ring beam lining a spring model, which is the horizon

46、tal beam-spring model of vertical migration to a tunnel structure (see Figure 3); vertical beam-spring model, each lining both Central by a straight line beam simulation, the lining of the joints between the rings to spring simulation, thus making a more longitudinal analysis of the calculation unit

47、, which can simulate the performance of lining of the Central and joints have changed the tunnel section, but its shortings are obvious, which means they are suitable for linear analysis, and due to the unit as a basis for analysis in matri* form, achieved through numerical methods, the results of a

48、n analysis of the need to get re-segment, bolts degree of stress and open joints and other key data . Another model is Shiba and Yukio Kawashima, Kazuhiko 23 25 as the representative of the equivalent a*ial stiffness model, the method considers that the tunnel in the horizontal for a homogeneous rin

49、g, in the longitudinal stiffness of the equivalent method in order to circumferential seams are non-continuous structure is equivalent to a continuous homogeneous cylinder. Because it is directly from the analysis of circumferential lining of joints and bolts of force-deformation properties of the s

50、tarting model to be equivalent, so the calculation results can be directly given segment and bolt stress, and in many cases can be derived by an e*plicit theoretical solution, application convenient, but the method has not taken into account pre-stressed, and simply be considered straight beam on el

51、astic foundation and other shortings, however, according to the current situation of the study at home and abroad, the a*ial equivalent stiffness method is the current theory of the tunnel structure of the longitudinal Research presented in the best way. The method to study the issue of Shield Tunne

52、l longitudinal laid a solid theoretical basis. 3 shield tunnel structure of assembled type Shield tunnel structure is a segment in the circumferential and longitudinal screw connections made through a non-continuous structure. As the pre-cast reinforced concrete segment economy, durability and high

53、strength, so be at home and abroad of the shield tunnel segment of the main form. Shield tunnel lining structure, assembly, there are two types: the wrong lining of joints assembled themselves and the assembled seam lining 10 11 12 19. These two different types of assembly is that; wrong lining of j

54、oints assembled adjacent ring segment due to structural stiffness between the different distribution along the ring, although the initial load are basically the same, but the structural deformation is different strata caused by anti - force is different from the different strata reaction e*acerbated

55、 by structural deformation of the difference. Because there is a link between adjacent rings, such as connecting bolts, torus bump Mortise and torus has hindered friction between the different structural deformation, so that the structure deformation and load and stratigraphic distribution of the di

56、fferent reactions within the scope be limited to a certain . Tong assembled lining the joints due to the adjacent ring segment between the structural rigidity along the circumferential distribution of the same, subject to the initial load are basically the same. Therefore, the structural deformation

57、 is basically the same, causing the formation reaction force is also basically the same. Although the assembled lining seam pass lateral deformation of each ring has also been mounted adjacent to Central and constraints, but the effects of constraints and the impact of the wrong seam sew more pronou

58、nced than the pass. This interaction between the lining ring is very ple*, sewing lining of the wrong calculation of internal forces and deformation is also more plicated, the calculation model and calculation method are also in-depth studies. In China, Shanghai in advance of construction of the shi

59、eld tunnel pass the basic use of sewing assembled form, the recent construction of the tunnel in Shanghai and Guangzhou, and Nanjing subway shield tunnel is used in all the wrong seam assembly form, which can show the wrong form of resistance to vertical seam assembly deformation is superior to pass

60、 suture assembled form. Since the assembly of different forms have different mechanical effects, can change the lining of the longitudinal stiffness and control of longitudinal cracks and uneven deformation, then the effect of the introduction of more mechanical assembly of different forms of soft s

61、oil on the solution to the current issue of shield tunnel structure, the other vertical key issues. 4 soft soil shield tunnel structural problems From the current engineering design of practical application and theoretical research can be drawn from analysis of the progress of soft soil shield tunne

62、l lining in considering the vertical structure of the inadequacies of problems: lack of theoretical and vertical close to the demand of the lining form; the e*isting theory of a lack of vertical and Engineering The bination of the real; lining assembled form of single (can not be reconciled vertical

63、ly non-uniform deformation); lining film material in the same project in a single; lining segment width of a single in the same project; vertical linear unreasonable. 5 Longitudinal Shield Tunnel in Soft Clay Design Forecast In order to overe the e*isting problems of soft soil shield tunnel, we must

64、 solve the following two aspects: (1) from the soft soil shield tunnel lining segment assembled form, tube sheet materials, innovation in areas such as transformation. In order to increase the soft soil shield tunnel lining structure of the longitudinal stiffness of the changes so that the soft soil

65、 shield tunnel lining structure of the longitudinal stiffness of a controllable. The different stiffness of the lining of the diverse forms of structural assembly to solve the problem of soft soil shield tunnel longitudinal possible. (2) In the longitudinal research and its application of design theory should be strengthened. Structural performance of tunnel